Last week around 1000 people turned out for our event at the Institute of Education to witness an armchair discussion between author and BHA vice-president Richard Dawkins and PZ Myers, American biology professor and the author of the blockbuster science blog Pharyngula.

This was a rare opportunity in the UK to see two leaders in their field pose questions to each other and informally discuss the topics about which they are so articulate and knowledgeable.

When the conversation turned to what evidence the speakers would need to be able to believe in the existence of a god, we felt like conspirators as Myers suggested that if he were to discover something that seems like a god, the scientist in him would want to cut it up and do research to
test it.

The evening ended on a very positive note, with Dawkins being asked how to ensure that young children are able to fully understand the wonder of biology and how we can ensure that they learn about it and be inspired. The conversation which ensued emphasised that we should ensure that children are able to experience all subjects, find the things that they feel passionate about, and be led by their own curiosity.

How do people defend their beliefs in bizarre conspiracy theories or the power of crystals? Philosopher Stephen Law has tips for spotting their strategies

You describe your new book, Believing Bullshit, as a guide to avoid getting sucked into "intellectual black holes". What are they?Intellectual black holes are belief systems that draw people in and hold them captive so they become willing slaves of claptrap. Belief in homeopathy, psychic powers, alien abductions - these are examples of intellectual black holes. As you approach them, you need to be on your guard because if you get sucked in, it can be extremely difficult to think your way clear again.

But isn't one person's claptrap another's truth?There's a belief system about water to which we all sign up: it freezes at 0 °C and boils at 100 °C. We are powerfully wedded to this but that doesn't make it an intellectual black hole. That's because these beliefs are genuinely reasonable. Beliefs at the core of intellectual black holes, however, aren't reasonable. They merely appear so to those trapped inside.

You identify some strategies people use to defend black hole beliefs. Tell me about one of them - "playing the mystery card"?This involves appealing to mystery to get out of intellectual hot water when someone is, say, propounding paranormal beliefs. They might say something like: "Ah, but this is beyond the ability of science and reason to decide. You, Mr Clever Dick Scientist, are guilty of scientism, of assuming science can answer every question." This is often followed by that quote from Shakespeare's Hamlet: "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy". When you hear that, alarm bells should go off.

But even scientists admit that they can't explain everything.There probably are questions that science cannot answer. But what some people do to protect their beliefs is to draw a veil across reality and say, "you scientists can go up to the veil and apply your empirical methods this far, but no further". Behind the veil they will put angels, aliens, psychic powers, God, ghosts and so on. Then they insist that there are special people who can see - if only dimly - through this veil. But the fact is that many of the claims made about things behind this veil have empirically observable consequences and that makes them scientifically testable.

How can science test these mysteries?Psychologist Christopher French at Goldsmiths, University of London, ran an experiment into the effects of crystals to explore claims that holding "real" crystals from a New Age shop while meditating has a powerful effect on the psyche, more so than just holding "fake" ones. But French found no difference in participants using real and fake crystals. This was good evidence that the effect people report is down to the power of suggestion, not the crystals.

Of course, this study provoked comments such as: "Not being able to prove the existence of something does not disprove its existence. Much is yet to be discovered." This is just a smokescreen. But because the mantra "it's-beyond-the-ability-of-science-to-establish..." gets repeated so often, it is effective at lulling people back to sleep - even if they have been stung into entertaining a doubt for a moment or two.

Do you think mystery has a place in science?Some things may be beyond our understanding, and sometimes it's reasonable to appeal to mystery. If you have excellent evidence that water boils at 100°C, but on one occasion it appeared it didn't, it's reasonable to attribute that to some mysterious, unknown factor. It's also reasonable, when we have a theory that works but we don't know how it works, to say that this is currently a mystery. But the more we rely on mystery to get us out of intellectual trouble, or the more we use it as a carpet under which to sweep inconvenient facts, the more vulnerable we are to deceit, by others and by ourselves.

In your book you also talk about the "going nuclear" tactic. What is this?When someone is cornered in an argument, they may decide to get sceptical about reason. They might say: "Ah, but reason is just another faith position." I call this "going nuclear" because it lays waste to every position. It brings every belief - that milk can make you fly or that George Bush was Elvis Presley in disguise - down to the same level so they all appear equally "reasonable" or "unreasonable". Of course, you can be sure that the moment this person has left the room, they will continue to use reason to support their case if they can, and will even trust their life to reason: trusting that the brakes on their car will work or that a particular drug is going to cure them.

Isn't there a grain of truth in this approach?There is a classic philosophical puzzle about how to justify reason: to do so, it seems you have to use reason. So the justification is circular - a bit like trusting a second-hand car salesman because he says he's trustworthy. But the person who "goes nuclear" isn't genuinely sceptical about reason. They are just raising a philosophical problem as a smokescreen, to give them time to leave with their head held high, saying: "So my belief is as reasonable as yours." That's intellectually dishonest.

You say we should also be aware of the "but it fits" strategy. Why?Any theory, no matter how ludicrous, can be squared with the evidence, given enough ingenuity. Every last anomaly can be explained away. There is a popular myth about science that if you can make your theory consistent with the evidence, then that shows it is confirmed by that evidence - as confirmed as any other theory. Lots of dodgy belief systems exploit this myth. Young Earth creationism - the view that the whole universe is less than 10,000 years old - is a good example. Given enough shoehorning and reinterpretation, you can make whatever turns up "fit" what the Bible says.

What about when people claim that they "just know" something is right?Suppose I look out the window and say: "Hey, there's Ted." You say: "It can't be Ted because he's on holiday." I reply: "Look, I just know it's Ted." Here it might be reasonable for you to take my word for it.

But "I just know" also gets used when I present someone with good evidence that there are, say, no auras, angels or flying saucers, and they respond: "Look, I just know there are." In such cases, claiming to "just know" is usually very unreasonable indeed.

What else should we watch out for?You should be suspicious when people pile up anecdotes in favour of their pet theory, or when they practise the art of pseudo-profundity - uttering seemingly profound statements which are in fact trite or nonsensical. They often mix in references to scientific theory to sound authoritative.

Why does it matter if we believe absurd things?It can cause no great harm. But the dangers are obvious when people join extreme cults or use alternative medicines to treat serious diseases. I am particularly concerned by psychological manipulation. For charlatans, the difficulty with using reason to persuade is that it's a double-edged sword: your opponent may show you are the one who is mistaken. That's a risk many so-called "educators" aren't prepared to take. If you try using reason to persuade adults the Earth's core is made of cheese, you will struggle. But take a group of kids, apply isolation, control, repetition, emotional manipulation - the tools of brainwashing - and there's a good chance many will eventually accept what you say.

Profile

Stephen Law is senior lecturer in philosophy at Heythrop College, University of London, and editor of the Royal Institute of Philosophy journal, Think. His latest book is Believing Bullshit: How not to get sucked into an intellectual black hole

Dublin Declaration on Secularism and the Place of Religion in Public Life

On Sunday 5 June 2011, the World Atheist Convention in Dublin discussed and adopted the following declaration on secularism and the place of religion in public life. Please discuss and promote it with your friends and colleagues, and if you are a a member of an atheist, humanist or secular group, please discuss and promote it with your fellow members, and with the media and politicians.

1. Personal Freedoms

(a) Freedom of conscience, religion and belief are private and unlimited. Freedom to practice religion should be limited only by the need to respect the rights and freedoms of others.
(b) All people should be free to participate equally in the democratic process.
(c) Freedom of expression should be limited only by the need to respect the rights and freedoms of others. There should be no right ‘not to be offended’ in law. All blasphemy laws, whether explicit or implicit, should be repealed and should not be enacted.

2. Secular Democracy

(a) The sovereignty of the State is derived from the people and not from any god or gods.
(b) The only reference in the constitution to religion should be an assertion that the State is secular.
(c) The State should be based on democracy, human rights and the rule of law. Public policy should be formed by applying reason, and not religious faith, to evidence.
(d) Government should be secular. The state should be strictly neutral in matters of religion and its absence, favouring none and discriminating against none.
(e) Religions should have no special financial consideration in public life, such as tax-free status for religious activities, or grants to promote religion or run faith schools.
(f) Membership of a religion should not be a basis for appointing a person to any State position.
(g) The law should neither grant nor refuse any right, privilege, power or immunity, on the basis of faith or religion or the absence of either.

3. Secular Education

(a) State education should be secular. Religious education, if it happens, should be limited to education about religion and its absence.
(b) Children should be taught about the diversity of religious and nonreligious philosophical beliefs in an objective manner, with no faith formation in school hours.
(c) Children should be educated in critical thinking and the distinction between faith and reason as a guide to knowledge. Science should be taught free from religious interference.

4. One Law For All

(a) There should be one secular law for all, democratically decided and evenly enforced, with no jurisdiction for religious courts to settle civil matters or family disputes.
(b) The law should not criminalise private conduct because the doctrine of any religion deems such conduct to be immoral, if that private conduct respects the rights and freedoms of others.
(c) Employers or social service providers with religious beliefs should not be allowed to discriminate on any grounds not essential to the job in question.